Wordpress: The uploaded file could not be moved to wp-content/uploads/

|Solution!| So basically after having a head-ache with permissions and ownership, I came across the final solution. I have a secure ftp user called ‘wp-user’ which I got from the tutorial here a while back. Apparently the fix is very simple, and it’s not a permissions issue.

During the set up process you define FTP Components in wp-config with the following lines:

define('FTP_PUBKEY','/home/wp-user/wp_rsa.pub');
define('FTP_PRIKEY','/home/wp-user/wp_rsa');
define('FTP_USER','wp-user');
define('FTP_PASS','');
define('FTP_HOST','127.0.0.1:22');

All you have to do is move those lines above the line which says:

/* That's all, stop editing! Happy blogging. */

Apparently the media uploader freaks out when the FTP Components are below that line, despite the plugin updater working fine. Hope this helps anyone who had this similar issue.